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McDonald's hopes someday all its beef will come from sustainable sources—but there's a lot of work standing between it and that lofty goal, CNBC reports. One key step: figuring out just what sustainable beef is. "There hasn't been a universal definition," the company says on its blog. McDonald's is joining forces with organizations like the World Wildlife Fund to create guidelines, and the chain plans to begin buying sustainable beef by 2016.

"We will focus on increasing the annual amount each year, but it is too early to predict the quantity that will be purchased in 2016," says a rep. "Beef represents our largest raw material purchase annually, and beef is our top priority." According to McDonald's own assessment last year, beef is behind some 28% of the company's greenhouse gas emissions. "We want to do our part to improve environmental practices in the way beef is produced, support positive workplaces in the beef industry, and drive continuous improvement in animal health and welfare," the spokeswoman notes. The fast-food giant has hada toughrun ofit lately. (Read more McDonald's stories.)